The invention concerns to a device relating to a cutting machine with an annular saw blade and with driving means for off-centre drive of the blade, comprising elements to clamp the blade in the cutting machine, which clamping means comprise two first rollers arranged to contact and to roll against the web of the saw blade on one side of the blade and two second rollers arranged to contact and to roll against the web of the blade on the other, opposite side of the blade. In the concept of cutting machines and saw blades, also saws and cutter wheels are included.
A device relating to a cutting machine according to the above is known through U.S. Pat. No. 4,472,880. As is shown in said US Patent there is a guiding groove in the web of the blade. A drive wheel for driving the blade is provided on the inside of the blade, the inner edge being bevelled in a wedge-shaped manner and pressed into a wedge-shaped groove with matching shape in the drive wheel. The above mentioned first or second rollers are, to accomplish this pressing-in, equipped with a flange which is engaged in the guiding groove and which is pressed against the inner edge of the guiding groove. Devices of the kind shown in U.S. Pat. No. 4,793,065 can be used in order to accomplish the necessary force acting on the guide rollers towards the centre of the blade.
The blade is conventionally clamped, in a direction which is parallel with the plane of the saw blade, i.e. in a radial direction, between on one hand the drive wheel which acts against the inner edge of the blade, and on the other hand the guide flanges on the first and second rollers which are equipped with such flanges and which in the following will be denoted guide rollers, said guide flanges acting in the guiding groove. The drive wheel and its wedge-shaped groove also has a clamping effect in the axial direction of the blade, that is across the plane of the blade. Said first and second rollers also cooperate in this axial clamping, which rollers act against the blade web and in a direction towards each other. It is important that the force of the rollers upon the blade web is sufficient in order to create enough friction to make the rollers roll and it is especially important that the guide roller is rotated by the blade. The pressing force must on the other hand not be too large. Tensions in the blade may occur in this case, which may lead to cracking and wreckage of the blade. The skilled man says that the blade is xe2x80x9crolledxe2x80x9d. It has not been investigated in detail why an excess contact pressure causes cracking, but it is believed that the generation of heat may play a role. Practical experience show, in any case, that the pressing force is the primary cause and that it is essential that the pressing force is adequate, i.e. not too large and not too small either. This has not been possible to accomplish in a satisfactory manner in prior art.
Another problem which not has been solved in a satisfactory manner according to prior art, is the journalling of and possibility to replace the rollers. This concerns the guide rollers as well as the rollers which act on the opposite side of the saw blade in relation to the guide rollers, in the following denoted support rollers.
It is a primary object of the invention to accomplish that the saw blade can be clamped between said first and second rollers with a not too small and not too large, in other words a suitable or optimal, clamping force.
It is also an object of the invention to make it possible to easily demount the rollers and to mount new rollers. It is, particularly, an object of this aspect of the invention that the ability to replace the rollers can be combined with the requirement concerning optimal clamping force, and vice versa.
In order to achieve the first objective, to accomplish a suitable clamping in the axial direction, the said device mentioned in the preamble is provided such that said first rollers are mounted on a first shaft, which is movable along a path against the plane of the saw blade, perpendicularly to the centre line of the shaft, for pressing said first rollers with a certain desired force against the blade web under counter force by the second rollers on the opposite side of the blade.
A preferred embodiment is characterised in that said first rollers are journalled on an eccentric journal, which like a crank journal is movable along a circular arc upon turning of an eccentric shaft, wherein spring means are arranged to turn the eccentric shaft, and fixing means are arranged to lock the eccentric shaft when said eccentric shaft has been turned such that the roller, which is journalled on the eccentric journal, is pressed against the web of the blade by means of the spring force. Also other embodiments, however, are conceivable within the scope of the invention. One can, for example, conceive that the shafts, on which said first rollers are journalled, can be arranged to be turnable in a pivot, whose axis of rotation is parallel with the rotational shaft of the rollers, and that said spring means are provided to accomplish the rotation in the pivot, and that said fixing means are arranged to lock a pivot journal or the like in the pivot, when said spring means has turned the corresponding roller to contact the saw blade.
Further characteristic features and aspects of the invention appear from the claims and the following detailed description of a preferred embodiment.